A aeração artificial em meio líquido visa suprir a baixa concentração de oxigênio dissolvido em ambientes deficientes deste, sendo um processo comumente aplicado na área de tratamento de efluentes por processos aeróbios. Uma forma de produzir aeração artificial é através de difusores submersos no fundo de um tanque com formação de bolhas, que ascendem e transferem seu oxigênio ao longo da coluna dágua. Para simular e melhor entender este processo e sua fluidodinâmica, um modelo inicial simplificado foi proposto, baseado em conceitos teóricos e equações que representem o fenômeno, como a de dispersão de bolhas, velocidades médias e concentração de oxigênio dissolvido. Foi considerado para realização dos cálculos um tanque retangular, com entrada de água a esquerda e saída de água a direita, com superfície sólida ao fundo e superfície livre acima, em contato com o ar. As equações de transporte de massa foram discretizadas no tempo, utilizando a técnica de Crank-Nicolson e no espaço segundo metodologia de diferenças centrais, solucionadas posteriormente por meio de técnicas iterativas do tipo Gauss-Seidel. As equações de transporte de quantidade de movimento foram resolvidas com o método MAC, explícito nas velocidades do fluido e implícito na pressão, para fornecer o campo de velocidade e pressão. A equação de que fornece o perfil de espalhamento das bolhas foi tomada como uma Equação Gaussiana de dispersão bidimensional. A implementação computacional necessária para aplicação das abordagens foi no ambiente de programação MATLAB. O método MAC e a técnica Crank-Nicolson apresentaram resultados satisfatórios para simulações rápidas e noção do comportamento do fluido e da concentração de oxigênio dissolvido. / The artificial aeration in aqueous mean aims to supply low concentration of dissolved oxygen in deficient atmospheres of it. This process is commonly applied in the field of wastewater treatment by aerobic processes. One way to produce artificial aeration is through diffusers submerged at the bottom of a tank with the formation of bubbles, which ascend and transfer its oxygen throughout the water column. To simulate and better understand this process and its fluid dynamics, a simplified initial model was proposed based on theoretical concepts and equations that represent the phenomenon, as the dispersion of bubbles, average speeds and dissolved oxygen concentration. It was considered for the calculations one rectangular tank with the water inlet and water outlet from left to right, with solid surface to the bottom and free surface at the top in contact with air. The mass transport equations were discretized in time, using the Crank-Nicolson technique and in space according to the methodology of central differences, subsequently resolved by Gauss-Seidel technique iterative. The transport equations of momentum were solved with the MAC method, explicit on the velocities of the fluid and implicit on pressure, to afford the velocity field and pressure. The equation which provides the spreading profiles of bubbles was taken as a two-dimensional Gaussian dispersion equation. The computational implementation necessary for application of the approaches was the programming environment MATLAB. The MAC method and Crank- Nicolson technique showed satisfactory results for quick simulations and notion of the behavior of the fluid and the concentration of dissolved oxygen.

Local and global loadings, which may cause the local damage and/or global failure and collapse of offshore structures and ships, are experimentally investigated in this study. The big research question is how the aeration of water and the elasticity of the structural section affect loading during severe environmental conditions. A further question is how the scattered waves from ships and offshore structures, the mooring line force and the structural response, which are known to affect local load and contribute to global load, will be affected by wave-structure interaction of a ship or offshore structure under non-breaking wave conditions. Three different experiments were undertaken in this study to try to answer these questions: (i) slamming impacts of a square flat rigid/elastic plate, which represents a plate section of the bottom or bow of ship structure, onto pure and aerated water surface with zero degree deadrise angle; (ii) wave impacts on a truncated vertical rigid/elastic wall in pure and aerated water, where the wall represents a plate section of a hull; and (iii) wave-structure interactions of different FPSO-shaped models, where the models were fixed or taut moored. The experiments were carried out at Plymouth University’s COAST Laboratory. Spatial impact pressure distributions on the square plate have been characterised under different impact velocities. It was found that the impact pressures and force in pure water were proportional to the square of impact velocity. There was a significant reduction in both the maximum impact pressure and force for slamming in aerated water compared to that in pure water. An exponential relationship of the maximum force and the void fraction is proposed and its coefficients are found from drop test in this study. There was also a significant reduction in the first phase of the pressure and force impulse for slamming into aerated water compared with pure water. On the truncated wall, aeration also significantly reduced peak wave loads (both pressure and force) but impulses were not reduced by very much. For the case considered here, elasticity of the impact plate has a significant effect on the impact loads, though only at high impact velocities; here the impact loads were considerably reduced with increasing elasticity. Wave loading on the truncated wall was found to reduce with increasing elasticity of the wall for all investigated breaking wave types: high aeration, flip-through and slightly breaking wave impacts. In particular, impact pressure decreases with increasing elasticity of the wall under flip-through wave impact. As elasticity increases, the impulse of the first positive phase of pressure and force decreases significantly. This significant effect of hydroelasticity is also found for the total force impulse on the vertical wall under wave impacts. Scattered waves were generated from the interaction of focused wave groups with an FPSO model. The results show that close to the bow of the FPSO model, the highest amplitude scattered waves are observed with the most compact model, and the third- and fourth-harmonics are significantly larger than the incident bound harmonic components. At the locations close to the stern, the linear harmonic was found to increase as the model length was decreased, although the nonlinear harmonics were similar for all three tested lengths, and the second- and third-harmonics were strongest with the medium length model. The nonlinear scattered waves increased with increasing wave steepness and a second pulse was evident in the higher-order scattered wave fields for the fixed and free floating models. In addition, the higher harmonics of the mooring line force, and the heave and pitch motions all increased with increasing wave steepness. Incident wave angles of 0 (head-on), 10 and 20 degrees were experimentally investigated in this study. As the incident wave angle between the waves and the long axis of the vessel was increased from 0 to 20 degrees, the third- and fourth-harmonic scattered waves reduced on the upstream side. These third- and fourth-harmonic diffracted waves are important in assessing wave run-up and loading for offshore structure design and ringing-type structural response in fixed and taut moored structures. The second-, third- and fourth-harmonics of the mooring line force, and the heave and pitch motions decreased as the incident wave angle increased from 0 to 20 degrees.

Esta dissertação trata da aeração induzida em vertedores com objetivo de mitigar os efeitos da cavitação sobre os mesmos. A análise bibliográfica do tema está calcada na introdução ao mecanismo da cavitação e no levantamento do estado da arte a partir dos trabalhos pioneiros, nos clássicos e nos recentes. Com base nos princípios da física: Conservação de Massa e Primeira Lei da Termodinâmica, foi desenvolvido um modelo matemático para aeração induzida em vertedores. O modelo proposto, após ser analisado do ponto de vista de sua consistência, foi avaliado em comparações com resultados fornecidos por outros pesquisadores, obtidos através de modelos físicos reduzidos. Os resultados obtidos pelo modelo matemático proposto correspondem a boas estimativas das grandezas envolvidas na aeração induzida em vertedores, o que credencia o modelo proposto como uma ferramenta apropriada para projetos de engenharia hidráulica e futuros desenvolvimentos científicos. / This study adress prompt aeration in spillways reaching to reduce the cavitation effects on them. References were based on introduction to cavitation machanism and, state of art survey, to leave on not only earlier studies, but also on classical and most recent ones. Based on principles of Physics, such as Mass Conservation and the First Law of Thermodynamics, a mathematical model has been developed as an example of prompt aeration in spillways. After extensive consistency analyses the proposed model has been validated by comparing different results furnished by studies on physical reduced models by other researchers. Results obtained from the mathematical model proposed here correspond to good estimates of greatnesses involved in prompt aeration is spillways and that turns the proposed model into an adequate tool for Hydraulic Engineering projects and for future scientifics stydies.

Chlorosis in plants has been recognized as a devastating disease for over one-hundred and fifty years. It is easily recognized by a yellowing of the plant foilage and is associated with a reduced chlorophyll synthesis. Chlorosis is found so frequently on calcareous soils that its cause is attributed at least in part to this soil factor. It is therefore referred to as lime-induced chlorosis. This type of chlorosis has become a serious problem, especially in many of the fruit-growing regions of Europe and the Western United States where the soils are calcareous. In Utah the disease is more destructive than any other nutritional disease that affect horticultural crops. The exact cause of lime-induced chlorosis is not known, nor has a satisfactory control been developed as yet. Many conditions found in high-lime soils have been studied with regard to chlorosis, yet the problem is not so simple as it may appear. Green and chlorotic plants are frequently found growing in the same field, and yet a chemical analysis of the two soils fails to indicate a significant difference between them. It is common in chlorotic orchards to see trees where some of the major branches produce chlorotic foilage while the remainder of the tree is healthy and green. The severity of chlorosis varies from tree to tree as well as from season to season. It has been found that the heavier textured soils which are poorly drained are more conductive to chlorosis than are the lighter textured soils. If the soil moisture is held near field capacity, chlorosis is much more severe than if the soil is allowed to approach the wilting point before irrigation. Recent studies have also shown that the bicarbonate ion in solution cultures can induce chlorosis and retard the uptake of iron by plants. Since these factors--high moisture, soil aeration, and bicarbonate ion concentration--are all interrelated, it seems that their relationship to chlorosis should be investigated more thoroughly. Workers in the past have failed to show a consistent correlation between either the oxygen or the carbon dioxide can be measured at the soil-root interface. this is after all the only place in the soil that is of great importance as far as the living plant is concerned. Since the severity of chlorosis increases under poorly aerated conditions on calcareous soils, this hypothesis has been advanced: The respired carbon dioxide is given off at the plant root as carbonic acid which in a calcareous soil reacts with calcium and magnesium carbonate to give an increased bicarbonate ion concentration in the root environment. The resulting increased concentration of bicarbonate may reduce the effective oxygen at the root and thereby disturb the normal respiration and active-ion absorption of the roots or the increased concentration of bicarbonate may affect the roots absorption and plant metabolism in some other manner. The purpose of this investigation was to study the effect of the bicarbonate ion and different aeration mixtures on chlorosis. A preliminary study was made to relate the composition of the soil solution taken from the field with different conditions associated with chlorosis.

Yeast are exposed to many physical and chemical stresses when used in large-scale industrial fermentations, particularly the initial stages in which yeast are shifted from anaerobic storage to aerated wort. This work investigated the transcriptional and physiological responses of yeast that had been shifted from anaerobic to aerobic growth conditions. Microarray technology was employed to determine the transcriptional changes that occurred in the first hour of a pilot-plant fermentation compared to the 23rd hour. It was found that over 100 genes were up-regulated initially including genes involved in the synthesis of the essential membrane sterol ergosterol and genes for the protection of cells against oxidative stress. It was also determined that cells which accumulate ergosterol precursors in the absence of ergosterol were more sensitive to exogenous oxidative stresses, indicating a role for ergosterol in oxidative stress tolerance. Aeration of anaerobically grown cells did not affect their growth kinetics or viability. However, anaerobically grown cells were hypersensitive to exogenous oxidative stress compared to their aerobic counterparts. Anaerobic cells that underwent a short period of aeration prior to treatment with hydrogen peroxide generated a tolerance to the oxidant, indicating that the period of aeration produced an adaptive-like response. Microarray analysis of the cells during the period of aeration showed that representative genes from the oxidative stress response family were up-regulated rapidly and it was determined that the response was controlled by the Yap1p and Skn7p transcription factors. Deletion of the transcription factor genes indicated that they were responsible for the creation of tolerance to oxidant. Target gene products of the two transcription factors (Gpx2p, Gsh1p and Trx2p) were shown to be induced during the shift to aeration; however, the glutathione redox balance did not seem to be affected as the cells were shifted from highly reduced to oxidising environments. Unexpectedly, it was discovered that genes involved in the synthesis of amino acids were up-regulated during anaerobic growth and stringently downregulated upon aeration of cells. The transcriptional activator of those genes (Gcn4p) was essential for growth in anaerobic media which included amino acid supplementation.

In the last years, due to an increasing concern about the possible harmful effects of the gas emissions of the continuous gasoline use, their compositions have changed considerably. The lead additives ban and the aromatic compounds content limitation has caused the worldwide expansion of the use of fuel oxygenates. These compounds are mainly molecules with an atom of oxygen inside its structure. Usually they are ethers or alcohols. The most used worldwide is methyl tert-butyl ether (MTBE) followed by ethyl tert-butyl ether (ETBE). These compounds because of their physical and chemical properties have become persistent and recalcitrant pollutants in the groundwaters of the entire world.Due to the problem generate by the contamination of water resources is important to go deeper in the knowledge of the behaviour of fuel oxygenates in the environment in order to obtain tools that let us model and study their environmental dispersion and remediation. This doctoral thesis offers an important thermodynamical study of these compounds and analyzes different remediation techniques.The work is structured in four chapter well differentiated. The first one consists of an introduction to the problem, the current situation of thermodynamical information and the existent techniques for the water treatment.The second chapter is focused on obtaining and improving the thermodynamical information. It is studied how temperature affect to the interactions of fuel oxygenates with different gasoline compounds such us BTEX (benzene, toluene, ethylbenzene and xylenes), alcans or degradation products like tert-butyl alcohol. In this chapter is included new thermodynamical information in terms of physical properties (density and speed of sound), vapor-liquid equilibria and liquid-liquid equilibria (as water solubility). As a result have been characterized 25 binary systems and their pure compounds in terms of physical property, 3 vapor liquid equilibria and finally the study of water solubility of the ethers most used in gasoline blending as temperature function.The third chapter is focused from a technological point of view. Here it is studied thermodynamically, different conventional remediation techniques fort he MTBE and ETBE like the adsorption onto activated carbon and batch air stripping. It is observed that the temperature increases the efficiency in both processes and that ETBE is easier treated. On the other hand, it has been analyzed the use of new solvents, in this case ionic liquids, in order to dehydrate fuel oxygenates obtaining satisfactory results. Finally, studies of advanced oxidation processes have been carried out using Fe-zeolites as catalyst. The use of these materials let oxidize MTBE and their most problematic degradation products, like tert-butyl alcohol and tert-butyl formate at environmental conditions and neutral pH in reasonable times.Finally in the fourth and last chapter are summarized the conclusions obtained during the development of this work and the research directions to follow in the future. / En els darrers anys, degut a una creixent preocupació sobre els possibles efectes nocius de les emissions de gasos procedents de l'ús continu de gasolines, la composició d'aquestes ha patit canvis importants. La prohibició dels additius amb plom així com la limitació de compostos aromàtics han donat lloc a una gran expansió arreu del món de l'ús del que es coneixen com additius oxigenats de la gasolina. Aquest compostos son principalment molècules que tenen dins la seva estructura almenys un àtom d'oxigen. Normalment acostumen a ser èters o alcohols. De tots els més utilitzats a nivell mundial son el metil tert butil èter (MTBE), seguit pel etil tert butil èter (ETBE). Aquests compostos degut a les seves propietats físiques i químiques han esdevingut uns contaminants persistents i recalcitrants de les aigues a tot el món.Degut a la problemàtica generada per la contaminació del recursos hídrics és important aprofundir en el coneixement del seu comportament en el medi ambient per tal de obtenir eines que permetin modelitzar i estudiar tant la seva dispersió com la seva remediació. La present tesi doctoral ofereix un estudi termodinàmic important d'aquest compostos i estudia diferents tècniques de remediació.Aquest treball s'estructura en quatre capítols ben diferenciats. El primer d'ells consisteix en una introducció a la problemàtica, la situació actual de la informació física i química de la qual es disposa i de les tècniques existents per al tractament d'aigües contaminades.El segon capítol està enfocat a obtenir i millorar la informació termodinàmica. S'estudia com la temperatura afecta a les interaccions dels additius oxigenats amb diferents constituents de les benzines com son els BTEX(benzè, toluè, etilbenzè i xilens), alcans o compostos de degradació dels oxigenats com pot ser el tert butil alcohol. En aquest capítol s'aporta nova informació termodinàmica prèviament no reportada en la literatura en termes de propietat físiques (densitat i velocitat de so), equilibri vapor líquid i equilibri líquid líquid (en forma de solubilitat en aigua). Com a resultat d'aquest capítol cal remarcar la caracterització de 25 sistemes binaris i els seus compostos purs en termes de propietat física, 3 equilibris binaris líquid vapor i finalment l'estudi de la solubilitat dels èters més utilitzats com additius oxigenats com a funció de la temperatura.El tercer capítol està enfocat des d'un punt de vista tecnològic. En aquest s'estudia termodinàmicament diferent tècniques convencionals per l'eliminació de MTBE i ETBE com son l'adsorció en carbó actiu i l'aireació. S'observa que l'increment de la temperatura augmenta l'eficiència en tot dos processos i que l'ETBE es més fàcilment eliminat. Per altra banda s'ha analitzat l'ús de nous solvents, com son els líquids iònics, per tal de deshidratar additius oxigenats obtenint-se resultats satisfactoris. Finalment s'han realitzat estudis d'oxidació avançada utilitzant zeolites amb contingut fèrric. L'ús d'aquest materials permet oxidar l'MTBE i els seus compostos de degradació més problemàtics, com son el tert butil alcohol i el tert butil formiat en condicions ambientals i pH neutres en temps raonables.Finalment en el quart i últim capítol es resumeixen les conclusions obtingudes durant aquest treball i es donen ressenyes a seguir en investigacions futures en aquest camp.

It has been confirmed that vented gases from swine manure compositing operations contain biodegradable ammonia and amines as main odorous compounds. The thesis focuses on the odor-removal performance from the gases by sparging them into an activated sludge aeration liquor in which the odorous compounds can be absorbed and biodegraded. An acrylic column (0.20 m i.d.¡Ñ1.2 mH) was used as the activated sludge aeration tank and a wooden case (1.0 mL¡Ñ0.6 mW¡Ñ0.6 mH) as a swine manure compositing tank. Seed sludge for the odor removal experiments was obtained from a swinery wastewater plant located at southern Taiwan. Both swine manure from the swinery and a pre-fermented composite sample obtained from a compositing plant located at East-southern Ping-Dong County were used for the odorous gas generation. Experiments were conducted at mixed liquor suspended solid (MLSS) concentrations of 2,250-2,750 mg/L, liquid pH of 6.4-6.6, and aeration intensities of 0.1-0.5 m3/m3.min. Results show that the experimental removal efficiencies for both ammonia and amines with, respectively, 18-50 and 180-250 ppm in the influent gas were greater than 80% with aerated activated sludge liquid depths of greater than 0.60 m within the tested aeration intensities. Keeping the activated sludge at around 25oC favored the biodegradation of the absorbed ammonia and amines and resulted in the removal of the compounds to around 85-95%. Temperatures of lower than 15oC shifted the removal to as low as 50-60% because of the limitations in both the biological growth and activity. Results from the study confirm that the activated sludge bioscrubbing approach should be applicable to odor control for the compositing plants.

Thesis (doctoral)--Swiss Federal Institute of Technology, Zurich, 1997. / Vita. Includes bibliographical references (p. 121-128).

Natural enrichment of ²³⁴U with respect to ²³⁸U was investigated in perched water, vadose zone pore waters, and secondary minerals. The activity ratio (AR) for dissolved ²³⁴U increased from about 1.4 in runoff to >6 in perched water. The AR in the vadose zone increased sharply at a transition that correlated with increased magnetic susceptibility and decreasing hydraulic conductivity. This was evidently caused by auto—oxidative selective leaching controlled by matrix saturation. The direct recoil fractionation mechanism has been proposed for tuffs on the Nevada Test Site, and could imply enhanced retardation of U. Direct recoil was evaluated using a steady state isotopic mass balance formulated to represent matrix pore water, and including first order sorption and selective leaching. Matrix sorption parameters were estimated by selectively leaching intact core with hydroxylamine. Much U was recovered, fractionated similarly to pore water. Interpreting this as isotopic exchange limited by Fickian transport within a sorbent layer, the rate constant and distribution coefficient were estimated. Uranium—series analysis of fracture—lining MnO₂ indicated that isotopic exchange was operant. The isotopic mass balance showed that direct recoil is a minor contribution to fractionation, so the predominant mechanism is selective leaching. This result depends mainly on the sorption rate constant, and where direct recoil is likely such as in roll—front deposits, it implies that the rate constant is smaller than in typical oxidizing waters. Extrapolating matrix properties to formation scale transport, an upper bound on formation scale sorption was inferred from the isotopic mass balance. Formation scale sorption is greater where the perched water table lies in more porous, permeable tuff. The layer diffusion model predicts that the effective sorption rate constant decreases significantly for thicker sorbent layers. Thus although fracture lining MnO₂ minerals are common at Yucca Mountain, U retardation may be strongly rate limited. Elevated AR's (>5) generally signify conditions favorable to U retardation, based on hydraulic isolation from recharge. Elevated vadose zone AR's do not necessarily signify the former presence of perched water, but could be interpreted that way at Yucca Mountain if similar fractionation is not found where past perching is unlikely.

Thesis (MTech. degree in Water Care ) - Tshwane University of Technology, 2007. / This research project investigated the total nitrogen removal capabilities of a nitrification and denitrification system treating two medium strength municipal landfill leachates. The characteristics of the leachates differed as one was obtained from general waste (GLB+) and the other from mixed industrial and general waste (H:h). This project was commissioned to develop a leachate treatment philosophy and a leachate management plan for the Vissershok landfill site near Cape Town. The aim of this leachate treatment trial project was to establish leachate treatability of different types of leachate, characterise leachate and effluent quality, determine alkalinity requirements, assess hydraulic retention periods and sludge production and confirm whether leachate quality can inhibit successful treatment in a sequencing batch reactor system. The two units were operated as simple Sequencing Batch Reactors (SBRs) by treating the leachate in a biological treatment process. Both units were initially seeded with activated sludge obtained from a sewage treatment works. Provision was made to supplement carbonaceous nutrient and phosphorus to the system. In the first stage of the study a controlled nitrification system was maintained to treat ammoniacal-nitrogen and the next stage denitrification was used to treat nitrate and nitrite-nitrogen levels. A completely automated daily cycle was used to treat the leachate and altered according to process requirements. The results showed that during nitrification ammoniacal-nitrogen concentrations as high as 2032.4 mg/l were consistently reduced to less than 0.1 mg/l. Similarly, for denitrification, nitrate-and nitrite-nitrogen concentrations were also consistently reduced to less than 0.1 mg/l, with a methanol utilisation ratio of CH3OH:N at 4.80:1. Chemical oxygen demand (COD) removal efficiencies were in the range 57-65% depending on loading rates applied. In conclusion it was shown that: (a) the biodegradable organics (COD) was reduced considerably (b) complete nitrification and denitrification occurred (c) no constituents of the leachate caused inhibition of the biological process.